The overall goal of this project is to determine whether arthroscopic meniscectomy in degenerative meniscal tears is beneficial from a clinical and scientific viewpoint relative to a non-meniscectomy surgical control. Arthroscopic meniscectomy is among the most commonly performed orthopedic surgical procedures in the VA system and nationally. 80% of patients in our practice having knee arthroscopy for meniscus tears have been in the 45-70 years age group and 53% of these patients had degenerative meniscal tears without a large unstable flap. These data are comparable of arthroscopic meniscectomy data drawn in other settings. However, there remains substantial uncertainty regarding the short term benefits and the long term consequences of arthroscopic meniscectomy in patients with degenerative meniscus tears. Degenerative meniscus tears are associated with osteoarthritis, and it is known that within two years of surgery, arthroscopic debridement for osteoarthritis is no better than placebo in relieving pain and restoring function. Longer term, meniscectomy has been shown to be associated with elevated risk of osteoarthritis development, raising the concern that meniscectomy can actually be harmful. It has also been shown by our group that patients with clinically successful arthroscopic posterior medial meniscectomy have significant change in the rotational motion of the knee during walking. Rotational changes at the knee follow soft tissue damage and have been implicated in the causes for cartilage degeneration. Thus there are critical unanswered questions regarding the clinical benefit as well as the scientific basis for arthroscopic meniscectomy for degenerative meniscal tear. To address these questions this project will conduct a prospective, randomized, blinded, and controlled study of arthroscopic meniscectomy in patients between the ages of 45 and 70 with stable degenerative meniscus tears. In this study, the control group will be a group of patients having arthroscopic lavage of the joint, but no debridement of a stable degenerative meniscus tear. The Aims will address clinical (self-reported) and scientific outcomes (functional) of arthroscopic meniscectomy in the time frame lasting up to two years after surgery. Aim 1: Test the clinical benefit of arthroscopic meniscectomy in the setting of a stable degenerative meniscus tear. Hypothesis 1a: There will be significant differences in WOMAC scores between the Meniscectomy and the Non-Meniscectomy/Lavage Groups at 12 months after surgery. Hypothesis 1b: The WOMAC scores of the Non-Meniscectomy/Lavage group will not be inferior to the WOMAC scores of the Meniscectomy group at 12 months after surgery Aim 2: Test the functional effect of arthroscopic meniscectomy in the setting of a degenerative meniscus tear. Hypothesis 2: Subjects randomized to arthroscopy and meniscectomy will have greater changes in tibio- femoral rotation, knee adduction moment, and knee flexion moment at 12 months following surgery when compared to subjects randomized to arthroscopy and lavage. We will also pursue other exploratory aims that are oriented towards understanding and characterizing the progression of incipient osteoarthritis from a clinical, biological, and radiographic standpoint. This prospective coordinated, multi-disciplinary approach will provide an important clinical and scientific assessment of arthroscopic meniscectomy that will improve treatment planning for degenerative meniscal tears. It will also provide new insight into incipient arthritis, yielding important information that will impact future patient care.